U.S. patent number 9,640,360 [Application Number 14/351,559] was granted by the patent office on 2017-05-02 for ion source and ion beam device using same.
This patent grant is currently assigned to Hitachi High-Technologies Corporation. The grantee listed for this patent is Hitachi High-Technologies Corporation. Invention is credited to Noriaki Arai, Yoshimi Kawanami, Shinichi Matsubara, Yoichi Ose, Hiroyasu Shichi.
United States Patent |
9,640,360 |
Shichi , et al. |
May 2, 2017 |
Ion source and ion beam device using same
Abstract
Provided is a charged particle beam microscope which has a small
mechanical vibration amplitude of a distal end of an emitter tip,
is capable of obtaining an ultra-high resolution sample observation
image and removing shaking or the like of the sample observation
image. A gas field ion source includes: an emitter tip configured
to generate ions; an emitter-base mount configured to support the
emitter tip; a mechanism configured to heat the emitter tip; an
extraction electrode installed to face the emitter tip; and a
mechanism configured to supply a gas to the vicinity of the emitter
tip, wherein the emitter tip heating mechanism is a mechanism of
heating the emitter tip by electrically conducting a filament
connecting at least two terminals, the terminals are connected by a
V-shaped filament, an angle of the V shape is an obtuse angle, and
the emitter tip is connected to a substantial center of the
filament.
Inventors: |
Shichi; Hiroyasu (Tokyo,
JP), Matsubara; Shinichi (Tokyo, JP), Ose;
Yoichi (Tokyo, JP), Kawanami; Yoshimi (Tokyo,
JP), Arai; Noriaki (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi High-Technologies Corporation |
Minato-ku, Tokyo |
N/A |
JP |
|
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Assignee: |
Hitachi High-Technologies
Corporation (Tokyo, JP)
|
Family
ID: |
48081854 |
Appl.
No.: |
14/351,559 |
Filed: |
October 10, 2012 |
PCT
Filed: |
October 10, 2012 |
PCT No.: |
PCT/JP2012/076161 |
371(c)(1),(2),(4) Date: |
April 12, 2014 |
PCT
Pub. No.: |
WO2013/054799 |
PCT
Pub. Date: |
April 18, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140299768 A1 |
Oct 9, 2014 |
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Foreign Application Priority Data
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Oct 12, 2011 [JP] |
|
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2011-224473 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J
27/022 (20130101); H01J 37/28 (20130101); H01J
37/26 (20130101); H01J 37/08 (20130101); H01J
2237/0807 (20130101); H01J 2237/0216 (20130101) |
Current International
Class: |
H01J
27/02 (20060101); H01J 37/08 (20060101); H01J
37/28 (20060101); H01J 37/26 (20060101) |
Field of
Search: |
;250/310 ;313/341 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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52-120673 |
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Oct 1977 |
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JP |
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58-085242 |
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May 1983 |
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JP |
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63-158730 |
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Jul 1988 |
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JP |
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05-198224 |
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Aug 1993 |
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JP |
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05-205680 |
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Aug 1993 |
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JP |
|
06-243776 |
|
Sep 1994 |
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JP |
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2006-269431 |
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Oct 2006 |
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JP |
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2008-091307 |
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Apr 2008 |
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JP |
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2008-175640 |
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Jul 2008 |
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JP |
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2009-517846 |
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Apr 2009 |
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JP |
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2009-163981 |
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Jul 2009 |
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JP |
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2009-164110 |
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Jul 2009 |
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JP |
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2009-289670 |
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Dec 2009 |
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JP |
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2013-118188 |
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Jun 2013 |
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JP |
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WO 03/031668 |
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Apr 2003 |
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WO |
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WO 2007/067328 |
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Jun 2007 |
|
WO |
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WO 2008/140080 |
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Nov 2008 |
|
WO |
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WO 2011/055521 |
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May 2011 |
|
WO |
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WO 2011/096227 |
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Aug 2011 |
|
WO |
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WO 2012/017789 |
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Feb 2012 |
|
WO |
|
Other References
Kuo, H.-S., et al., "Preparation and Characterization of Single
Atom Tips", Nano Letters, vol. 4, No. 12, 2004, pp. 2379-2382.
cited by applicant .
Morgan, J. , et al., "An Introduction to the Helium Ion
Microscope", Microscopy Today, vol. 14, No. 4, Jul. 2006, pp.
24-31. cited by applicant.
|
Primary Examiner: Stoffa; Wyatt
Attorney, Agent or Firm: Miles & Stockbridge P.C.
Claims
The invention claimed is:
1. A gas field ion source comprising: an emitter tip configured to
generate ions; an emitter-base mount configured to support the
emitter tip; a mechanism configured to heat the emitter tip; an
extraction electrode installed to face the emitter tip and
configured to include an opening allowing the ions to pass
therethrough; and a mechanism configured to supply a gas to the
vicinity of the emitter tip, wherein the emitter tip heating
mechanism is a mechanism of heating the emitter tip by electrically
conducting a filament which has a shape of a straight line
connecting at least two terminals, connection points between the
terminals and the filament is connected by the filament at an
approximately shortest distance, and the emitter tip is connected
to a substantial center of the filament, and wherein a second wire
material connects the at least two terminals and the second wire
material and the filament are connected to a base portion of the
emitter tip.
2. The gas field ion source according to claim 1, wherein a
substantial central portion of the extraction electrode has a
convex structure.
3. The gas field ion source according to claim 1, wherein the
filament is made of manganin.
4. The gas field ion source according to claim 1, wherein the
filament is subjected to ceramic coating.
5. The gas field ion source according to claim 1, wherein the
filament has a structure where localized resistivity of the
substantial central portion of the filament is relatively high.
6. A gas field ion source, wherein the gas supplied to the gas
field ion source according to claim 1 contains at least one of
hydrogen, helium, neon, argon, krypton, and xenon.
7. A gas field ion source, wherein the emitter tip of the gas field
ion source according to claim 1 is configured in a shape of a
nano-pyramid.
8. The gas field ion source according to claim 7, wherein a distal
end of said emitter tip has 4 or more and less than 10 atoms.
9. The gas field ion source of claim 1, further comprising a
soundproof cover configured to separate spatially a compressor
connected to a refrigeration system for cooling an emitter tip of
the gas field ion source.
10. The gas field ion source of claim 1, wherein the natural
frequency of an installation structure of the emitter tip is 5000
Hz or more.
11. The gas field ion source according to claim 1, wherein said gas
field ion source is configured to provide a magnification of
projection of an ion beam on a sample of at least 0.5 or more.
Description
TECHNICAL FIELD
The present invention relates to a charged particle microscope and
an ion microscope, and more particularly, to a gas field ion source
and an ion beam device.
BACKGROUND ART
The surface structure of a sample can be observed by scanning and
irradiating the sample with an electron beam and detecting
secondary charged particles emitted from the sample. This is called
a "scanning electron microscope" (hereinafter referred to as a
SEM). On the other hand, the surface structure of a sample can also
be observed by scanning and irradiating the sample with an ion beam
and detecting secondary charged particles emitted from the sample.
This is called a "scanning ion microscope" (hereinafter, referred
to a SIM). Particularly, the irradiation of the sample with ion
species with light mass such as hydrogen, helium, or the like makes
a sputtering function become relatively small, so that the
irradiation is suitable for sample observation.
The ion beam has a characteristic of being sensitive to information
on the surface of the sample in comparison to the electron beam.
This is because the excited area of secondary charged particles is
localized according to the surface of the sample in comparison to
the irradiation with the electron beam. In addition, with respect
to the electron beam, since the properties of electrons as a wave
cannot be neglected, aberration occurs due to the diffraction
effect. On the other hand, with respect to the ion beam, since the
ion is heavier than the electron, the aberration due to the
diffraction effect is very small in comparison with the electron
beam.
If the electron beam is irradiated on the sample and the electrons
that have transmitted through the sample are detected, information
on the internal structure of the sample can be obtained. Similarly,
if the ion beam is irradiated on the sample and the ions that have
transmitted through the sample are detected, information on the
internal structure of the sample can also be obtained. This is
called a transmission ion microscope. Particularly, the irradiation
of the sample with ion species with light mass such as hydrogen,
helium, or the like makes a ratio of transmission through the
sample become large, so that the irradiation is suitable for sample
observation.
On the contrary, the irradiation of the sample with ion species
with heavy mass such as oxygen, nitrogen, argon, krypton, xenon,
gallium, indium, or the like is suitable for sample processing due
to the sputtering function. Particularly, a focused ion beam
apparatus (hereinafter, referred to as an FIB) using a liquid metal
ion source (hereinafter, referred to as an LMIS) is known as an ion
beam processing apparatus. In addition, a plasma ion source or a
gas field ion source may generate gas ions of oxygen, nitrogen,
argon, krypton, xenon, or the like and the gas ions are irradiated
on the sample, so that the sample processing can be performed.
In an ion microscope mainly for the sample observation, the gas
field ion source is very suitable as an ion source. In the gas
field ion source, gas such as hydrogen or helium is supplied to a
metal emitter tip having a curvature radius of about 100 nm at the
distal end, and a high voltage of several kilo voltages or more is
applied to the emitter tip, so that the gas molecules are
field-ionized, and the ionized molecules are extracted as an ion
beam. The ion source has a characteristic that, since an ion beam
having a narrow energy width can be generated and a size of the ion
source is small, a minute ion beam can be generated.
In the ion microscope, in order to observe the sample at a high
signal-to-noise ratio, an ion beam having a high current density
needs to be obtained on the sample. For this reason, an ion
radiation angular current density of the gas field ion source needs
to be high. In order to increase the ion radiation angular current
density, the emitter tip may be cooled down to a very low
temperature. PTL 1 discloses that a minute protrusion is formed at
a distal end of an emitter tip so as to improve characteristics of
an ion source. NPL 1 discloses that a minute protrusion at a distal
end of an emitter tip is made of a second metal different from a
material of the emitter tip. NPL 2 discloses a scanning ion
microscope equipped with a gas field ion source emitting helium
ions.
PTL 2 discloses a structure which is configured to include an
emitter for a charged particle beam is provided to first and second
supporting portions, a filament extending therebetween, an emitter
distal end portion provided to the filament, and a stabilization
element provided for a third supporting portion and the filament,
wherein the first, second, third supporting portions defines a
triangle, so that the stabilization element at least partly extends
in a direction perpendicular to the extension direction of the
filament. According to the structure, a vibration amplitude of the
emitter distal end portion is suppressed, so that resolution of a
charged particle beam apparatus employing the emitter can be
improved.
PTL 3 disclose an electronic source including a needle-shaped tip
having an electron emission portion at one end, a cup-shaped part
jointed to the other end of the needle-shaped tip different from
the one end thereof, and a filament for heating the cup-shaped
part, wherein the filament is disposed in an air gap defined inside
the cup-shaped part so as not to be connected to the cup-shaped
part. Although external vibration is applied to an apparatus using
the electronic source, the apparatus can emit a stabilized electron
beam.
PTL 4 discloses a structure of an electronic source where a pair of
conductive terminals are provided for an insulator, a tip having an
electron radiation portion is bonded to a filament attached between
the conductive terminals, and the other end of the tip different
from the electron radiation portion is fixed to the insulator, a
structure of an electronic source where the other end of the tip
different from the electron radiation unit is fixed to the
insulator through a metal pin soldered to the insulator; and a
structure of an electronic source where a curved portion is
provided to the filament. Although external vibration is applied to
an apparatus using the electronic source, the apparatus can emit a
stabilized electron beam.
PTL 5 discloses a structure of a gas field ion source where a
filament is supported by a plurality of pillars, for example 3, 4,
5, or 6 pillars. Sensitivity of an emitter to mechanical vibration
can be reduced.
In addition, PTL 6 discloses a thermal field emission electron gun
which is characterized in that, in a thermal field emission cathode
capable of radiating a stabilized electron beam effective to the
purpose of a high speed electron beam exposure apparatus or the
like, a filament for heating a needle-shaped electrode has a
structure of a V shape, and an angle of the V shape is in a range
of 30 degrees to 90 degrees.
CITATION LIST
Patent Literature
PTL 1: JP 58-85242 A PTL 2: JP 2006-269431 A PTL 3: WO 2008-140080
A PTL 4: JP 2008-91307 A PTL 5: JP 2009-517846 W PTL 6: JP
06-243776 A
Non-Patent Literature
NPL 1: H.-S. Kuo, I.-S. Hwang, T.-Y. Fu, J.-Y. Wu, C.-C. Chang, and
T. T. Tsong, Nano Letters 4 (2004) 2379. NPL 2: J. Morgan, J.
Notte, R. Hill, and B. Ward, Microscopy Today, Jul. 14, 2006 24
SUMMARY OF INVENTION
Technical Problem
The gas field ion source where a distal end of the metal emitter
tip has a structure of a nano-pyramid has the following problems.
The characteristic of the ion source is to use ions emitted from
the vicinity of one atom at the distal end of the nano-pyramid.
Namely, the area of ion emission is narrow, and the size of the ion
beam is as small as nanometers or less. Therefore, the current per
unit area and unit solid angle, that is, brightness is high. If the
ion beam is condensed on the sample with the same magnification, or
if the ion beam is condensed on the sample with the contraction
ratio of several fractions, the beam diameter of, for example,
about 0.1 nm to 1 nm can be obtained. Namely, observation with
ultra-high resolution of about 0.1 nm to 1 nm can be implemented.
Herein, it is possible to obtain a characteristic in that the
diameter of the ion beam on the projected image is increased as the
magnification is increased; and however, the obtained current is
also increased. If the current is increased, there is an advantage
in that the signal-to-noise ratio of the image can be increased,
and the image acquisition time can be shortened. Namely, it is
possible to obtain a characteristic in that, although the
magnification is large, since the diameter of the ion beam is as
small as nanometers or less, the diameter of the ion beam on the
projected image can also be limited to be less than 1 nm, and the
current is large. This is also different from the situation of an
ultra-high resolution scanning electron microscope including a
field emission type electron gun. Although the diameter of the beam
of the field emission type electron gun is as small as the order of
nanometers, since the diameter is larger than that of a gas field
ion source, the magnification is set to be 1/10 or less in order to
obtain a sub-nanometer resolution.
If the distal end of the emitter tip is mechanically vibrated, the
ion beam on the sample is also vibrated. This causes deterioration
in resolution or shaking in an image of the sample observation.
Particularly, as described above, this influence is great in the
case of use under the condition that the magnification is large.
For example, in the case where the magnification is 1, when the
vibration amplitude of the distal end of the emitter tip is 1 nm,
the ion beam on the sample is vibrated by 1 nm. This means that
great deterioration in resolution or shaking of an image occurs in
a sub-nanometer resolution image. Therefore, in comparison with a
scanning electron microscope in the related art, in the ion
microscope, reducing the mechanical vibration amplitude of the
distal end of the emitter tip is one of the most important
problems.
An object of the present invention is to provide an ion microscope
and a charged particle beam apparatus capable of implementing a
small mechanical vibration amplitude of a distal end of the emitter
tip and ultra-high resolution observation without shaking or the
like in a sample observation image.
Solution to Problem
The present invention is a gas field ion source including: an
emitter tip configured to generate ions; an emitter-base mount
configured to support the emitter tip; a mechanism configured to
heat the emitter tip; an extraction electrode installed to face the
emitter tip and configured to include an opening allowing the ions
to pass therethrough; and a mechanism configured to supply a gas to
the vicinity of the emitter tip, wherein the emitter tip heating
mechanism is a mechanism of heating the emitter tip by electrically
conducting a filament connecting at least two protrusion terminals,
the terminals are connected by a V-shaped filament, an angle of the
V shape is an obtuse angle, and the emitter tip is connected to a
substantial center of the filament.
In addition, connection points between the terminals and the
filament is connected by the filament at an approximately shortest
distance, and the emitter tip is connected to a substantial center
of the filament.
In addition, the filament has a shape of a straight line.
In addition, in the gas field ion source, a second wire material
connecting at least two terminals besides the filament exists, and
the emitter tip is connected to the filament and the second wire
material.
In addition, the emitter tip heating mechanism is a mechanism of
heating the emitter tip by electrically conducting a filament
connecting at least two terminals, the emitter tip is connected to
a substantial center of the filament, in the case where a
temperature of the emitter tip is relatively low, the emitter tip
is connected to the terminals excluding the two terminals, and in
the case where the temperature of the emitter tip is relatively
high, the emitter is not connected.
In addition, in the gas field ion source, a substantial central
portion of the extraction electrode has a convex structure.
In addition, in the gas field ion source, the cross section of the
filament has a U shape, a V shape, or a hollow tube shape.
In addition, in the gas field ion source, the filament is made of
manganin.
In addition, in the gas field ion source, the filament is subjected
to ceramic coating.
In addition, in the gas field ion source, the filament has a
structure where localized resistivity of the substantial central
portion of the filament is relatively high.
In addition, in the gas field ion source, the structure where the
localized resistivity is relatively high has a locally V shape or a
locally U shape.
In addition, the gas supplied to the gas field ion source contains
at least one of hydrogen, helium, neon, argon, krypton, and
xenon.
In addition, the emitter tip of the gas field ion source is
configured in a shape of a nano-pyramid.
In addition, in a charged particle beam apparatus equipped with the
gas field ion source, a magnification of projection of an ion beam
on a sample is at least 0.5 or more.
In addition, there is provided an ion beam device which is equipped
with a gas field ion source and scans and irradiates a sample with
an ion beam emitted from the gas field ion source and detects
secondary particles emitted from the sample to obtain a sample
observation image, wherein image shaking does not occur in the
sample observation image with a resolution higher than the maximum
resolution of a field ionization emission type scanning electron
microscope.
Advantageous Effects of Invention
According to the present invention, in a charged particle beam
microscope, it is possible to allow a mechanical vibration
amplitude of a distal end of an emitter tip to be small, to obtain
an ultra-high resolution sample observation image, and to remove
shaking or the like in a sample observation image.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic diagram illustrating a configuration of an
example of a charged particle microscope according to the present
invention.
FIG. 2 is a diagram illustrating an example of a peripheral
structure of an emitter tip of a gas field ion source of the
charged particle microscope according to the present invention.
FIGS. 3(A) to 3(C) are diagrams illustrating an example of a
peripheral structure of an emitter tip of a gas field ion source of
the charged particle microscope according to the present
invention.
FIG. 4 is a schematic diagram illustrating a configuration of a
control system of an example of the charged particle microscope
according to the present invention.
FIGS. 5(A) to 5(C) are schematic diagrams illustrating an example
of a scanned ion image obtained by the charged particle microscope
according to the present invention.
FIGS. 6(A) to 6(D) are diagrams illustrating an example of a
peripheral structure of an emitter tip of a gas field ion source of
the charged particle microscope according to the present
invention.
FIG. 7 is a diagram illustrating an example of a peripheral
structure of an emitter tip of a gas field ion source of the
charged particle microscope according to the present invention.
FIG. 8 is a schematic diagram illustrating a configuration of an
example of the charged particle microscope according to the present
invention.
FIGS. 9(A) and 9(B) are diagrams illustrating an example of a
peripheral structure of an emitter tip of a gas field ion source of
the charged particle microscope according to the present
invention.
FIG. 10 is a diagram illustrating an example of a peripheral
structure of an emitter tip of a gas field ion source of the
charged particle microscope according to the present invention.
FIG. 11 is a diagram illustrating an example of the charged
particle microscope according to the present invention.
DESCRIPTION OF EMBODIMENTS
First Embodiment
An example of a charged particle microscope according to the
present invention will be described with reference to FIG. 1.
Hereinafter, a first embodiment of a scanning ion microscope
apparatus as an ion beam apparatus will be described. The scanning
ion microscope according to the embodiment is configured to include
a gas field ion source 1, an ion beam irradiation system column 2,
a sample chamber 3, and a cooling mechanism 4. Herein, the gas
field ion source 1, the ion beam irradiation system column 2, and
the sample chamber 3 are a vacuum chamber.
Although the configuration of the gas field ion source 1 will be
described later in detail, a needle-shaped emitter tip 21 and an
extraction electrode 24 provided to face the emitter tip and to
include an opening 27 through which ions pass are included within a
vacuum chamber 68. An ionization chamber 15 is provided to increase
a pressure of ionized gases in the vicinity of the emitter tip. A
gas supply pipe 25 provided at the front end of a gas supply
mechanism 76 is connected to the ionization chamber 15 to supply
the ionized gases to the vicinity of the emitter tip.
In addition, an ion source vacuum exhaust pump 12 is provided to
vacuum-exhaust the vacuum chamber 68 of the gas field ion source 1.
A vacuum cutoff valve 69 is disposed between the vacuum chamber 68
and the ion source vacuum exhaust pump 12.
In addition, a vacuum pump 71 containing non-evaporable getters 70
is connected to the vacuum chamber 68 of the gas field ion source
1. In addition, a heating mechanism 72 outside the vacuum chamber
is provided to the non-evaporable getters 70. The heating mechanism
is based on the principle of resistive heating, lamp heating, or
the like.
A vacuum cutoff valve 74 is disposed between the vacuum pump 71
containing the non-evaporable getters 70 and the vacuum chamber 68.
In addition, a vacuum pump 78 is connected to the vacuum pump 71
containing the non-evaporable getters 70 through a vacuum cutoff
valve 77.
Furthermore, the gas field ion source 1 includes a tilting
mechanism 61 which changes a tilt of the emitter tip 21, and the
tilting mechanism 61 is fixed to an emitter-base mount 64. The
tilting mechanism 61 is used for accurately adjusting the direction
of the distal end of the emitter tip to an ion beam irradiation
axis 14A. Due to the adjustment of the angle of the axis, it is
possible to obtain an effect of reducing distortion of the ion
beam.
In addition, the ion beam irradiation system is configured to
include a condenser lens 5 which condenses ions emitted from the
gas field ion source 1, a first aperture 6 which is movable and
limits an ion beam 14 passing through the condenser lens 5, a first
deflector 35 which scans or aligns the ion beam 14 passing through
the first aperture 6, a second deflector 7 which deflects the ion
beam 14 passing through the first aperture 6, a second aperture 36
which limits the ion beam 14 passing through the first aperture 6,
and an objective lens 8 which condenses the ion beam passing
through the first aperture on the sample.
In addition, although not illustrated, in some cases, a mass
separator may be provided to the ion beam irradiation system. In
addition, in some cases, a mechanism capable of tilting the
condenser lens with respect to the ion beam irradiation axis 14A
may be provided. The tilting mechanism 61 may be implemented as a
relatively compact mechanism by using piezoelectric elements.
Herein, the first deflector 35 is a deflector which scans the ion
beam in order to obtain an ion radiation pattern from the emitter
tip. In addition, the "first" denotes that the defector is located
at the first position in the direction from the ion source 1 to the
sample 9. However, a charged particle beam apparatus may be
configured such that a deflector which is shorter than the length
of the first defector 35 in the optical axis direction is provided
between the first deflector 35 and the condenser lens 5, and the
deflector is used to adjust the deflection axis of the ion beam
14.
In addition, a sample stage 10 which the sample 9 is mounted on and
a secondary particle detector 11 are installed within the sample
chamber 3. The ion beam 14 from the gas field ion source 1 is
irradiated on the sample 9 through the ion beam irradiation system.
The secondary particles from the sample 9 are detected by the
secondary particle detector 11. Herein, the signal amount measured
by the secondary particle detector 11 is almost proportional to the
ion beam current passing through the second aperture 36.
The ion microscope according to the embodiment is configured to
further include a sample chamber vacuum exhaust pump 13 which
vacuum-exhausts the sample chamber 3. In addition, although not
illustrated, an electron gun for neutralizing charge-up of the
sample occurring at the irradiation of ion beam or a gas gun for
supplying etching or deposition gas to the vicinity of the sample
is provided to the sample chamber 3.
In addition, a base plate 18 is disposed through an anti-vibration
mechanism 19 on the equipment stand 17 disposed on the floor 20.
The field ion source 1, the column 2, and the sample chamber 3 are
supported by the base plate 18.
The cooling mechanism 4 cools the interior of the field ion source
1, the emitter tip 21, the extraction electrode 24, and the like.
In the embodiment, the cooling path is disposed in the inner
portion of the emitter-base mount 64. In addition, in the case
where the cooling mechanism 4 is configured by using, for example,
Gifford-McMahon type (GM type) refrigerator, a compressor unit
(compressor) which uses a helium gas as an operating gas (not
illustrated) is installed on the floor 20. The vibration of the
compressor unit (compressor) is transmitted through the floor 20 to
the equipment stand 17. An anti-vibration mechanism 19 is disposed
between the equipment stand 17 and the base plate 18 and has a
characteristic of allowing high-frequency vibration of the floor
not to be easily transmitted to the field ion source 1, the ion
beam irradiation system column 2, the sample chamber 3, and the
like. In the embodiment, as a source of vibration of the floor 20,
the refrigerator 40 and the compressor 16 are exemplified. However,
the source of vibration of the floor 20 is not limited thereto.
The anti-vibration mechanism 19 may be configured by using an
anti-vibration rubber, a spring, a damper, or a combination
thereof.
An example of the gas field ion source 1 of the charged particle
microscope according to the present invention will be described in
detail with reference to FIG. 2. The gas field ion source 1
according to the embodiment is configured to include a
needle-shaped emitter tip 21, a thin-wire filament 22, two
pillar-shaped terminals 26, a cylindrical filament mount 23, and a
cylindrical emitter-base mount 64.
FIG. 3(A) is a pictorial diagram of the cylindrical filament mount
23 as viewed from the emitter tip side. The needle-shaped emitter
tip 21 is connected to an approximate center of the thin-wire
filament 22. The thin-wire filament 22 is V-shaped in FIG. 3(A) and
is connected between the two pillar-shaped terminals 26. FIG. 3(B)
is a front diagram, and the angle of the V shape of the filament 22
is an obtuse angle. FIG. 3(C) is a side diagram. As described
above, the apparatus according to the embodiment has a structure of
allowing the vibration from the floor 20 or the like not to be
easily transmitted to the ion source. However, it is found out
through the mechanical vibration simulation of this structure that
the filament 22 is shaken sideways as illustrated in FIG. 3(C) by
the influence of the noise on the ion source. In addition, it is
found out the vibration amplitude depends on the angle of the V
shape and the vibration amplitude is decreased when the angle is
not an acute angle of about 60 degrees of the related art but an
obtuse angle as in the present invention. Particularly, when the
angle is about 100 degrees or more, the vibration reducing effect
is greatly improved in comparison with the related art.
The filament mount 23 is fixed to the emitter-base mount 64 with an
insulating material or the like interposed therebetween. By doing
so, the emitter tip 21 can be applied with a high voltage. An
operating exhaustion hole 67 which the ion beam is to pass through
is formed on the ion source vacuum chamber 68.
The field ion source according to the embodiment is configured to
further include an extraction electrode 24 and a cylindrical
sidewall 28. The extraction electrode 24 is disposed to face the
emitter tip 21 and has the opening which the ion beam 14 is to pass
through. The extraction electrode can be applied with a high
voltage.
A space surrounded by the extraction electrode 24, the sidewall 28,
and the filament mount 23 is called a gas molecule ionization
chamber 15.
In addition, a gas supply pipe 25 at the distal end of the gas
supply mechanism 76 is connected to the gas molecule ionization
chamber 15. A to-be-ionized gas (ionized gas) is supplied to the
emitter tip 21 through the gas supply pipe 25.
In the embodiment, the to-be-ionized gas (ionized gas) is helium.
In addition, the cooling mechanism of the emitter tip 21 is not
presented in FIG. 2.
FIG. 4 illustrates an example of controllers of the ion microscope
according to the present invention illustrated in FIG. 1. The
controllers according to the embodiment include a field ion source
controller 91 which controls the gas field ion source 1, a
refrigerator controller 92 which controls the refrigerator 4, a
temperature controller 191 which controls the heating mechanism 72
for the non-evaporable getters 70, the cooling mechanism 4, and the
like, a valve controller 192 which controls opening and closing of
a plurality of the vacuum cutoff valves 69, 74, and 77 disposed in
the vicinity of the gas field ion source, a lens controller 93
which controls the condenser lens 5 and the objective lens 8, a
first aperture controller 94 which controls the first aperture 6
which is movable, a first deflector controller 195 which controls
the first deflector, a second deflector controller 95 which
controls the second deflector, a secondary electron detector
controller 96 which controls the secondary particle detector 11, a
sample stage controller 97 which controls the sample stage 10, a
vacuum exhaust pump controller 98 which controls the sample chamber
vacuum exhaust pump 13, and a computing device 99 which includes an
arithmetic unit. The computing device 99 is configured to include
an image display unit. The image display unit displays images
generated from detection signals of the secondary particle detector
11 and information input by an input means.
The sample stage 10 is configured to include a mechanism of
straightly moving the sample 9 in the two perpendicular directions
within the sample mounting plane, a mechanism of straightly moving
the sample 9 in the direction vertical to the sample mounting
plane, and a mechanism of rotating the sample 9 within the sample
mounting plane. The sample stage 10 further has a tilting function
of changing the irradiation angle of the ion beam on the sample 9
by rotating the sample 9 about the tilting axis. The control is
performed by the sample stage controller 97 according the
instruction from the computing device 99.
Next, the operations of the field ion source according to the
embodiment will be described. In the description herein, helium is
employed as an ionized gas. When a sufficient time elapses after
vacuum exhaustion, the refrigerator 4 is driven. Accordingly, the
emitter tip 21, the extraction electrode 24, and the like are
cooled down.
Next, the structure of the emitter tip 21 and the manufacturing
method thereof will be described. First, a tungsten wire having a
diameter of about 100 to 400 .mu.m and an axis orientation
<111> is prepared, and the distal end is formed to be sharp.
Accordingly, the emitter tip 21 having a distal end of which radius
of curvature is several tens of nanometers can be obtained. In
another vacuum chamber, iridium is vacuum-deposited on the distal
end of the emitter tip 21. Next, the emitter tip 21 is heated at
high temperature by electrically conducting the filament 22, so
that the iridium atoms are moved to the distal end of the emitter
tip 21. Accordingly, a pyramid structure in the order of nanometer
is formed by the iridium atoms. This structure is called a
nano-pyramid. The nano-pyramid typically has one atom at the distal
end, a three- or six-atom layer as an underlying layer thereof, and
a ten-or-more-atom layer as an underlying layer thereof.
Herein, the inventors of the present invention have found that the
temperature in the emitter tip heating by electrically conducting
the filament 22 needs to be controlled with good reproducibility in
order to form the nano-pyramid with good reproducibility. In
addition to the heating characteristic of the filament 22 as a
single body, the dissipation of the heat of the filament needs to
be considered. However, in the case of cooling down to a cryogenic
temperature as the ion source 1 according to the embodiment, the
influence is particularly great. This means that the condition of
the heating control of the emitter tip of the electron gun or the
ion source in the related art is different from the condition of
the heating control of the emitter tip of the ion source according
to the embodiment. As described above, the V shape of the filament
22 greatly influences the mechanical vibration characteristic, and
similarly, the V shape of the filament 22 influences the heating
characteristic of the emitter tip 21.
Although a thin wire of tungsten is used in the embodiment, a thin
wire of molybdenum may be used. In addition, although a coat of
iridium is used, a coat of platinum, rhenium, osmium, palladium,
rhodium, or the like may be used.
In addition, as a method of forming the nano-pyramid at the distal
end of the emitter tip 21, field evaporation in vacuum, gas
etching, ion beam irradiation, or the like may be used. According
to these methods, a nano-pyramid of tungsten atoms or molybdenum
atoms can be formed at the distal end of a tungsten wire or a
molybdenum wire. For example, in the case of using a <111>
tungsten wire, it is characterized in that the distal end is
configured with one or three atoms of tungsten. In addition,
alternatively, the same nano-pyramid may be formed at the distal
end of a thin wire of platinum, iridium, rhenium, osmium,
palladium, rhodium, or the like by an etching process in vacuum.
The emitter tip having a sharp distal structure in the atomic order
is called a nano-tip.
As described above, the characteristic of the emitter tip 21 of the
gas field ion source according to the embodiment is based on the
nano-pyramid. By adjusting the electric field intensity formed at
the distal end of the emitter tip 21, helium ions can be generated
in the vicinity of one atom of the distal end of the emitter tip
21. Therefore, the area where the ions are emitted, that is, the
ion beam source is a very narrow area, of which the size is
nanometer or less. In this manner, by generating the ions from a
very limited area, the beam diameter can be limited to 1 nm or
less. For this reason, the current value per unit area and unit
solid angle of the ion source is increased. This is an important
characteristic for obtaining an infinitesimal-diameter and large
current ion beam on the sample.
In addition, in the case where one-atom nano-pyramid is formed at
the distal end by using platinum, rhenium, osmium, iridium,
palladium, rhodium, or the like, similarly current emitted from
unit area and unit solid angle, that is, ion source brightness can
be increased, so that it is suitable for reducing the beam diameter
on the sample of the ion microscope or increasing the current.
However, in the case where the emitter tip is sufficiently cooled
down and gas is sufficiently supplied, it is not necessary to form
the single atom at the distal end, but sufficient performance can
be obtained with three, six, seven, ten, or more atoms.
Particularly, it has been found that, in the case where the distal
end is formed with four or more atoms and less than ten atoms, the
ion source brightness can be increased, and the stable operation
can be performed so as to allow the atoms at the distal end not to
be easily evaporated.
Next, a voltage is applied between the emitter tip 21 and the
extraction electrode 24. A strong electric field is formed at the
distal end of the emitter tip. The helium supplied from the gas
supply pipe 25 is pulled to the emitter tip surface by the strong
electric field. The helium reaches the vicinity of the distal end
of the emitter tip 21 where the strongest electric field exists.
The helium is field-ionized at the site, so that helium ion beam is
generated. The helium ion beam is guided to the ion beam
irradiation system through a hole 27 of the extraction electrode
24.
Next, operations of the ion beam irradiation system of the ion
microscope according to the embodiment will be described. The
operations of the ion beam irradiation system are controlled by
instructions from the computing device 99. The ion beam 14
generated by the gas field ion source 1 is condensed by the
condenser lens 5, the beam diameter of the ion beam is limited by
the beam limiting aperture 6, and the ion beam source is condensed
by the objective lens 8. The condensed beam is scanned and
irradiated on the sample 9 on the sample stage 10. Herein, the
large current acquisition condition is used where the magnification
of the condensation of the ion beam on the sample by the condenser
lens and the objective lens is at least 0.5 or more. By doing so,
it is possible to increase the current relative to the beam
diameter and to increase a signal-to-noise ratio of a scanned ion
image.
The secondary particles emitted from the sample are detected by the
secondary particle detector 11. The signal from the secondary
particle detector 11 is brightness-modulated by the secondary
electron detector controller 96 to be transmitted to the computing
device 99. The computing device 99 generates a scanning ion
microscope image and displays the image on the image display unit.
By doing so, high resolution observation on the sample surface can
be implemented.
FIGS. 5(A) to 5(C) are schematic diagrams illustrating an
ultra-high resolution observation image of a sample surface. The
sample has a structure of two straight lines. In FIG. 5(A), it is
observed that, when the distal end of the emitter tip mechanically
vibrates, edges of the two straight lines are shaken. In FIG. 5(B),
it is observed that, when the distal end of the emitter tip
mechanically vibrates and the ion beam scanning frequency is low,
the edges of the two straight lines are blurry. FIG. 5(C) is a
schematic diagram illustrating an ultra-high resolution observation
image obtained in the state where the apparatus according to the
embodiment normally operates. In this figure, it is observed that
the edges of the two straight lines are clear. This is an effect
obtained by reduction in vibration amplitude of the distal end of
the emitter tip by forming the filament to be in a V shape and
setting the angle of the V shape to an obtuse angle. As a result,
it is possible to obtain a resolution of about 0.2 nm which is an
aberration of the lens in the scanned ion image of the sample
surface.
In addition, in FIG. 6(A) illustrating another embodiment, the
connection points between the pillar-shaped terminals 26 and the
filament 21 are connected by the filament 22 at approximately
shortest distance, and the emitter tip 21 is connected to the
approximate center of the filament 22.
FIG. 6(A) is a pictorial diagram of the cylindrical filament mount
23 as viewed from the emitter tip 21 side. FIG. 6(B) is a front
diagram, in which the filament has a shape of a straight line and
the emitter tip 21 is connected to the approximate center thereof.
In the embodiment, it is also possible to obtain a resolution of
about 0.2 nm which is an aberration of the lens in the scanned ion
image of the sample surface. However, in order to stabilize the
heating characteristic of the filament, a process of increasing the
interval of the filament terminals to increase the length of the
filament 22, or adding a stabilizing circuit to the control circuit
is needed. In addition, if small deformation of a U shape or a V
shape is applied to the approximate center, the localized
resistivity of the substantial central portion of the filament 22
is relatively increased, so that it is possible to obtain an effect
in that, it is suitable for heating the filament 22 up to high
temperature and it is possible to reduce the mechanical vibration
amplitude at the distal end of the emitter tip 21. In addition, by
using the ion beam apparatus of scanning and irradiating the sample
9 with the ion beam 14 emitted from the gas field ion source 1 and
detecting the secondary particles emitted from the sample to obtain
the sample observation image, it is possible to obtain an effect of
obtaining an ultra-high resolution sample observation image and an
effect capable of removing shaking or the like in the sample
observation image.
In addition, as illustrated in a side diagram of FIG. 6(C), it has
found that the emitter tip 21 itself is slightly shaken. Therefore,
in FIG. 7 illustrating another embodiment, the filament 22 has a
shape of a straight line, and besides the filament 22, a second
wire material 29 connecting at least two terminals exists, and the
base portion of the emitter tip 21 is connected to the filament 22
and the second wire material 29. By doing so, slight vibration of
the emitter tip 21 itself is also successfully reduced. As a
result, the aberration of the lens is improved, so that it is
possible to obtain a resolution of about 0.1 nm.
In addition, as illustrated in FIG. 7, it is characterized in that
the substantial central portion of the extraction electrode 24 has
a convex structure 31 toward the emitter tip 21. By doing so, the
distance between the two terminals and the extraction electrode is
increased, discharge or the like does not occur between the two
terminals and the extraction electrode, so that it is possible to
obtain an effect of increasing in reliability.
In the embodiment described hereinbefore, it is possible to obtain
an effect capable of reducing the mechanical vibration amplitude of
the distal end of the emitter tip. In addition, by using the ion
beam apparatus of scanning and irradiating the sample 9 with the
ion beam emitted from the gas field ion source 1 and detecting the
secondary particles emitted from the sample to obtain the sample
observation image, it is possible to obtain an effect of obtaining
an ultra-high resolution sample observation image and an effect
capable of reducing shaking, blur, or the like in the sample
observation image.
In addition, if an external magnetic field is shield by configuring
the field ion source 1, the ion beam irradiation system, and the
vacuum chambers such as the sample chamber 3 with magnetic
materials, the diameter of the ion beam is decreased, so that it is
possible to obtain an effect of implementing higher resolution
observation.
In addition, as described in the embodiment, if the emitter tip of
the gas field ion source 1 is configured in a nano-pyramid, an ion
beam having an infinitesimal beam diameter and large current can be
obtained, so that it is possible to obtain an effect of obtaining
an ultra-high resolution sample observation image with a high
signal-to-noise ratio and it is possible to remove shaking or the
like in the sample observation image.
In addition, in the charged particle beam apparatus equipped with
the gas field ion source 1, by using the charged particle beam
apparatus characterized in that the magnification of the ion beam
projected on the sample is at least 0.5 or more, it is possible to
obtain an effect in that the ion beam current is particularly
increased; and by using the ion beam apparatus of scanning and
irradiating the sample 9 with the ion beam emitted from the gas
field ion source 1 and detecting the secondary particles emitted
from the sample to obtain the sample observation image, it is
possible to obtain an effect of obtaining an ultra-high resolution
sample observation image with a high signal-to-noise ratio and an
effect capable of removing shaking or the like in the sample
observation image.
In addition, in the case of the apparatus configured by omitting
the tilting mechanism 61 which changes the tilt of the emitter tip,
it is possible to reduce the distortion of the ion beam at the
condenser lens 5 by adjusting the tilt of the condenser lens 5
according to the direction of the ion beam emitted from the distal
end of the emitter tip, and thus, the diameter of the ion beam is
decreased, so that it is possible to obtain an effect of
implementing higher resolution observation. In addition, since the
tilting mechanism of the emitter tip 21 can be omitted, it is
possible to obtain an effect capable of simplifying the structure
of the ion source and furthermore implementing a low-cost
apparatus.
In addition, an ion emission pattern of the emitter tip 21 is
observed by another vacuum apparatus, and the tilting direction of
the emitter tip 21 is accurately adjusted, and after that, if it is
introduced into the apparatus according to the embodiment, it is
possible to omit the tilting mechanism 61 which changes the tilt of
the emitter tip 21 or to reduce the tilting range. By doing so, it
is possible to obtain an effect capable of simplifying the
structure of the ion source and furthermore implementing a low-cost
apparatus.
In addition, according to the embodiment hereinbefore, in the
above-described gas field ion source, the distal end of the emitter
tip 21 is formed in a nano-pyramid configured with atoms, so that
the ionization area is limited, and thus, the ion source 1 having
higher brightness is formed, so that it is possible to perform
higher resolution sample observation. In addition, at this time,
since the total ion current is decreased, the ionized gas is
circulated and reused, so that it is possible to obtain an effect
of providing a gas field ion source having a higher use efficiency
of the ionized gas.
Although the helium gas is employed in the embodiment, hydrogen,
neon, argon, krypton, xenon, or other gases may be employed in the
present invention. By doing so, if hydrogen or helium is used, it
is possible to obtain an effect in that an infinitesimal surface of
the sample can be observed by the ion beam; and if neon, argon,
krypton, or xenon is used, it is possible to obtain an effect in
that the ion beam becomes suitable for the sample processing with
the ion beam, and the mechanical vibration amplitude of the distal
end of the emitter tip can be further reduced.
Second Embodiment
Next, an example of the charged particle beam apparatus according
to the embodiment will be described with reference to FIG. 8. In
FIG. 8, the cooling mechanism 4 of the charged particle beam
apparatus illustrated in FIG. 1 will be described in detail. In the
example, the cooling mechanism 4 employs a helium circulation
type.
The cooling mechanism 4 according to the embodiment cools the
helium gas as a coolant by using a GM type refrigerator 401 and
heat exchangers 402, 405, 409, and 412 and circulates the cooled
helium gas by the compressor unit 400. The helium gas compressed
at, for example, 0.9 MPa by the compressor and having a room
temperature of 300 K is allowed to flow into the heat exchanger 402
through the pipe 409 and exchanges heat with the low-temperature
backward helium gas to be described later to be cooled down to a
temperature of about 60 K. The cooled helium gas is transported
through the pipe 403 in the insulated transfer tube 404 to flow
into the heat exchanger 405 disposed in the vicinity of the gas
field ion source 1. Herein, by cooling the heat conduction material
thermally integrated with the heat exchanger 405 down to a
temperature of about 65 K, the above-described shield reducing the
thermal radiation is cooled down. The heated helium gas is allowed
to flow out the heat exchanger 405 and to flow through the pipe 407
into the heat exchanger 409 thermally integrated with the first
cooling stage 408 of the GM type refrigerator 401 to be cooled down
to a temperature of about 50 K and to be allowed to flow into the
heat exchanger 410. The helium gas exchanges heat with the
low-temperature backward helium gas to be described later to be
cooled down to a temperature of about 15K, and after that, is
allowed to flow into the heat exchanger 412 thermally integrated
with the second cooling stage 411 of the GM type refrigerator 401
to be cooled down to a temperature of about 9 K. The cooled helium
gas is transported through the pipe 413 in the transfer tube 404 to
flow into the heat exchanger 414 disposed in the vicinity of the
gas field ion source 1, so that the cooling conduction bar 53 which
is a good heat conduction material thermally connected to the heat
exchanger 414 is cooled down to a temperature of about 10 K. The
helium gas heated by the heat exchanger 414 is allowed to
sequentially flow through the pipe 415 into the heat exchangers 410
and 402 and exchanges the above-described helium gas to be heated
up to almost a room temperature of about 275 K, and the helium gas
is recovered through the pipe 415 to the compressor unit 400. In
addition, the above-described low-temperature portion is contained
in a vacuum heat-insulating container 416, and the transfer tube
404 is adiabatically connected although not shown. In addition, in
the vacuum heat-insulating container 416, although not shown, an
irradiation shield plate, a laminated heat-insulating material, or
the like prevents heat intrusion due to radiation heat from the
room temperature portions into the low temperature portions.
In addition, the transfer tube 404 is firmly fixed to and supported
by the floor 20 or a supporting body 417 installed on the floor 20.
Herein, although not shown, the pipes 403, 407, 413, and 415 where
glass fibers having a low heat conductivity are fixed to and
supported by a heat-insulating body made of plastic in the transfer
tube 404 are also fixed to and supported by the floor 20. In
addition, in the vicinity of the gas field ion source 1, the
transfer tube 404 is fixed to and supported by the base plate 18,
and similarly, although not shown, the pipes 403, 407, 413, and 415
where glass fibers having a low heat conductivity are fixed to and
supported by a heat-insulating body made of plastic in the transfer
tube 404 are also fixed to and supported by the base plate 18.
Namely, the cooling mechanism is configured with a cold generating
means which generates a cold by expanding a first high pressure gas
generated by the compressor unit 16 and a cooling unit which
performs cooling by using the cold of the cold generating unit and
cools the cooling object by using a helium gas as a second
transporting coolant circulating to the compressor unit 400.
The cooling conduction bar 53 is connected to the emitter tip 21
through a deformable copper stranded wire (a wire consisting of a
bundle of 100 copper wires each having a diameter of 50 .mu.m) 54
and a sapphire base. By doing so, cooling of the emitter tip 21 is
implemented. In the embodiment, although the GM type refrigerator
401 causes the floor to vibrate, the gas field ion source 1, the
ion beam irradiation system column 2, the vacuum sample chamber 3,
and the like are installed so as to be isolated from the GM type
refrigerator 401, it is characterized in that, since the pipes 403,
407, 413, and 415 connected to the heat exchangers 405 and 414
installed in the vicinity of the gas field ion source 1 are firmly
fixed to and supported by the floor 20 or the base 18 which does
not almost vibrate and are further vibration-isolated from the
floor, it is possible to implement a system where the transmission
of mechanical vibration is very small.
Next, the structure of the vicinity of the emitter tip according to
the embodiment will be described. FIGS. 9(A) and 9(B) are
perspective diagrams illustrating the cylindrical filament mount 23
as viewed from the emitter tip side.
In the gas field ion source 1, it is characterized in that, the
emitter tip heating mechanism 72 is a mechanism of heating the
emitter tip 21 by electrically conducting the filament 22
connecting at least two terminals 26; the emitter tip 21 is
connected to the substantial center of the filament 22; in the case
where the emitter tip temperature is relatively low, as illustrated
in FIG. 9(A), the emitter tip 21 is connected to the terminal
excluding the two terminals 26; and in the case where the emitter
tip temperature is relatively high, as illustrated in FIG. 9(B),
the emitter tip 21 is not connected to the terminals excluding the
two terminals.
By doing so, in the case where the emitter tip temperature is
relatively low, since the emitter tip is connected to the terminal
excluding the two terminals 26, it is possible to obtain an effect
capable of reducing the mechanical vibration amplitude of the
distal end of the emitter tip. Herein, if the emitter tip
temperature is low, it is possible to obtain an effect in that the
ion beam current is increased. In addition, in the case where the
emitter tip temperature is high, since the emitter tip is not
connected to the terminals excluding the two terminals 26, it is
possible to obtain an effect where the heat is not dissipated at
the time of heating the filament and the heating control accuracy
is improved. In addition, by using the ion beam apparatus of
scanning and irradiating the sample 9 with the ion beam emitted
from the gas field ion source 1 and detecting the secondary
particles emitted from the sample 9 to obtain the sample
observation image, it is possible to obtain an effect of obtaining
a further ultra-high resolution sample observation image and an
effect capable of removing shaking or the like in the sample
observation image.
In addition, in another embodiment, the gas field ion source 1 is
characterized in that the cross section of the filament 22 has a U
shape, a V shape, or a hollow tube shape.
In addition, in another embodiment, the gas field ion source 1 is
characterized in that the filament 22 is made of manganin.
In addition, in another embodiment, the gas field ion source 1 is
characterized in that ceramic coating is performed on the filament
22.
By doing so, since the rigidity of the filament 22 is further
increased, the vibration amplitude of the filament becomes small,
so that it is possible to obtain an effect of allowing the
mechanical vibration amplitude of the distal end of the emitter tip
to be small. In addition, by using the ion beam apparatus of
scanning and irradiating the sample 9 with the ion beam emitted
from the gas field ion source 1 and detecting the secondary
particles emitted from the sample 9 to obtain the sample
observation image, it is possible to obtain an effect of obtaining
a further ultra-high resolution sample observation image and an
effect capable of removing shaking or the like in the sample
observation image.
In addition, in another embodiment, as illustrated in FIG. 10, the
structure is used where the emitter tip 21 is directly connected to
the filament mount 23 but not connected to the filament 22. The
emitter tip heating is implemented by applying a voltage between
the emitter tip 21 and the filament 22 to emit electrons from the
filament 22 to the emitter tip 21 after the heating of the filament
22. In this structure, the vibration of the filament is not
transmitted to the emitter tip.
In this manner, by using the ion beam apparatus of scanning and
irradiating the sample 9 with the ion beam further emitted from the
gas field ion source and detecting the secondary particles emitted
from the sample 9 to obtain the sample observation image, it is
possible to obtain an effect of obtaining an ultra-high resolution
sample observation image and an effect capable of removing shaking
or the like in the sample observation image.
In addition, the ion beam apparatus is characterized in that, in
the ion beam apparatus which is equipped with the gas field ion
source 1 and scans and irradiates the sample 9 with the ion beam 14
emitted from the gas field ion source 1 and detects the secondary
particles emitted from the sample 9 to obtain the sample
observation image, when a sound wave having a frequency of 5000 Hz
or more is irradiated toward the ion beam apparatus, shaking occurs
in the sample observation image. By doing so, since the natural
frequency of the installation structure of the emitter tip is 5000
Hz or more, the vibration transmitted from the floor or the like
cannot be easily transmitted to the emitter tip.
In addition, as illustrated in FIG. 11, an effect of a site where a
soundproof cover 418 of cutting off sound is provided is further
improved.
In this manner, by using the ion beam apparatus of scanning and
irradiating the sample with the ion beam further emitted from the
gas field ion source and detecting the secondary particles emitted
from the sample to obtain the sample observation image, it is
possible to obtain an effect of obtaining an ultra-high resolution
sample observation image and an effect capable of removing shaking
or the like in the sample observation image.
In addition, by using the ion beam apparatus which is characterized
in that, in the ion beam apparatus which is equipped with the gas
field ion source and scans and irradiates the sample with the ion
beam emitted from the gas field ion source and detects the
secondary particles emitted from the sample to obtain the sample
observation image, image shaking does not occur in the sample
observation image with a resolution higher than the maximum
resolution of a field ionization emission type scanning electron
microscope, it is possible to obtain an effect of obtaining an
ultra-high resolution sample observation image and an effect of
removing shaking or the like in the sample observation image.
In addition, according to the gas field ion source and the charged
particle beam apparatus of the present invention, the vibration
from the cooling mechanism is not easily transmitted to the emitter
tip and the fixing mechanism of the emitter-base mount is provided,
so that the vibration of the emitter tip can be prevented, and high
resolution observation can be performed.
Further, the inventors of the present invention have found that the
noise of the compressors 16 and 400 illustrated in FIG. 8 causes
the gas field ion source 1 to vibrate, so that the resolution is
deteriorated. Therefore, in the embodiment, the cover 418 is
provided to separate the compressors 16 and 400 and the gas field
ion source 1 in spatial. By doing so, it is possible to reduce the
influence of the vibration caused by noise of the compressors 16
and 400, so that it is possible to implement high resolution
observation.
In addition, although a second helium gas is circulated by using
the helium compressor 400 in the embodiment, although not
illustrated, flow regulating valves are provided, and the pipes 111
and 112 of the helium compressor 16 and the pipes 409 and 415 are
connected to each other through the flow regulating valves; and a
portion of the helium gas of the helium compressor 16 in the pipe
409 is supplied as the second helium gas which is a circulating
helium gas, and the gas is recovered through the pipe 415 to the
helium compressor 16, so that the same effect can be obtained.
In addition, although the GM type refrigerator 401 is used in the
embodiment, a pulse tube refrigerator or stirling type refrigerator
may be used instead of the GM type refrigerator, and it is not
limited to a type of a refrigerator. Although the refrigerator has
two cooling stages in the embodiment, the refrigerator may have a
single cooling stage, and the number of cooling stages is not
particularly limited. For example, by using a helium circulating
refrigerator which uses small-sized stirling type refrigeration
having one cooling stage and of which the lowest cooling
temperature is 50 K, it is possible to implement a compact, and
low-cost ion beam apparatus. In this case, instead of the helium
gas, a neon gas or hydrogen may be used. In addition, a plurality
of the refrigerators may be used.
In addition, it is found out that, in the embodiment, if the helium
compressor 400 is stopped at the time of acquiring the scanned ion
image, noise of the scanned ion image is reduced, so that it is
possible to obtain a clear and high-resolution image. In this case,
during the time when the temperature of the ion emitter does not
cause a great change in current, the helium is circulated by
driving the helium compressor 400, so that the temperature is
decreased. According to the method, it is found out that the effect
of noise reduction is easily obtained in comparison with stopping
the operation of the refrigerator at the time of acquiring the
scanned ion image. In addition, it is found out that, if the
operations of the helium compressor and the refrigerator are
stopped, the noise is further reduced, so that it is possible to
obtain a clear and high-resolution image.
Third Embodiment
Next, a charged particle microscope capable of observing a sample
surface, performing sample processing, and observing an internal
portion of the sample to perform complex analysis of the sample by
using a hybrid particle source which has a distal end of an emitter
tip formed in a nano-pyramid configured with atoms and extracts an
ion beam or electrons from the needle-shaped emitter tip will be
described with reference to FIG. 11.
The same configurations as those of the first and second
embodiments will be omitted in description.
The charged particle microscope according to the embodiment is
configured to include a hybrid particle source 301 which has a
distal end of an emitter tip formed in a nano-pyramid configured
with atoms and extracts an ion beam or electrons from a
needle-shaped emitter tip, a hybrid irradiation system 302 which
irradiates a sample with the electron beam and the ion beam, a
sample stage 303, a secondary particle detector 304 which detects
secondary particles emitted from the sample, an optical system 305
which forms an image from charged particles that have transmitted
through the sample, and the like.
Herein, any one of positive and negative high voltage power
supplies can be selectively connected to the emitter tip. Namely,
in the case of applying the positive high voltage, a positive ion
beam can be extracted from the emitter tip; and in the case of
applying the negative high voltage, an electron beam can be
extracted from the emitter tip. In addition, at least two or more
types of gases can be introduced into the hybrid particle source.
Namely, at least two types of gases including one of hydrogen and
helium and at least one of neon, argon, krypton, xenon, nitrogen,
and oxygen can be introduced.
In the charged particle microscope, any one of the ion beams of
neon, argon, krypton, xenon, nitrogen, and oxygen can be extracted
from the emitter tip, and the sample processing can be performed by
irradiating the sample with the ion beam. In addition, the sample
surface can be observed by using one of the ion beams of hydrogen
and helium extracted from the needle-shaped emitter tip. In
addition, the electrons can be extracted from the needle-shaped
emitter tip, and the electrons are irradiated on the sample to form
an image of the electrons that have transmitted through the sample,
so that it is possible to obtain internal information of the
sample. By doing so, it is possible to perform complex analysis of
the sample without exposure of the sample to the atmosphere.
In the embodiment hereinbefore, in the hybrid charged particle
microscope configured to include the hybrid particle source which
has a distal end of the emitter tip formed in a nano-pyramid
configured with atoms and extracts an ion beam or electrons from
the needle-shaped emitter tip, the charged particle irradiating
optical system which guides the charged particles from the hybrid
particle source to the sample, the secondary particle detector
which detects the secondary particles emitted from the sample, the
charged particle image forming optical system which forms an image
from the charged particles that have transmitted through the
sample, and a gas supply pipe which supplies gases to the vicinity
of the emitter tip, wherein the gases are selected as two or more
types of gases including one of gases of hydrogen and helium and
any one of gases of neon, argon, krypton, xenon, nitrogen, and
oxygen, and wherein any one of positive and negative high voltage
power supplies can be selectively connected to the needle-shaped
emitter tip, it is possible to obtain an effect of providing a
charged particle microscope capable of observing an infinitesimal
surface of the sample by using one of ion beams of hydrogen and
helium, capable of performing sample processing by using any one of
the ion beams of neon, argon, krypton, xenon, nitrogen, and oxygen,
and capable of observing an internal portion of the sample by
irradiating the sample with an electron beam and detecting the
electrons that have transmitted through the sample. Particularly,
since an ion beam having an infinitesimal diameter and an electron
beam having an infinitesimal diameter can be obtained by using the
nano-pyramid emitter tip, it is possible to obtain an effect of
providing a charged particle microscope capable of performing
sample information analysis in the order of sub-nanometer.
In addition, in the embodiment hereinbefore, in a hybrid charged
particle beam microscope method, wherein a distal end of an emitter
tip is in a nano-pyramid configured with atoms, wherein any one of
ion beams of neon, argon, krypton, xenon, nitrogen, and oxygen is
extracted from the needle-shaped emitter tip and is irradiated on
the sample to perform sample processing, wherein one of ion beams
of hydrogen and helium is extracted from the needle-shaped emitter
tip and is used to observe the sample surface, and wherein
electrons are extracted from the needle-shaped emitter tip and are
irradiated on the sample to form an image of electrons that have
transmitted through the sample to obtain internal information of
the sample, it is possible to obtain an effect capable of observing
the sample surface, performing sample processing, and observing an
internal portion of the sample to perform complex analysis of the
sample. Particularly, by using the nano-pyramid emitter tip, it is
possible to obtain an effect of providing a charged particle
microscope method capable of performing sample information analysis
using an ion beam having an infinitesimal diameter and an electron
beam having an infinitesimal diameter.
REFERENCE SIGNS LIST
1 gas field ion source 2 ion beam irradiation system column 3
sample chamber 4 cooling mechanism 5 condenser lens 6 movable
aperture 7 deflector 8 objective lens 9 sample 10 sample stage 11
secondary particle detector 12 ion source vacuum exhaust pump 13
sample chamber vacuum exhaust pump 14 ion beam 14A optical axis 15
gas molecule ionization chamber 16 compressor 17 equipment stand 18
base plate 19 anti-vibration mechanism 20 floor 21 emitter tip 22
filament 23 filament mount 24 extraction electrode 25 gas supply
pipe 26 terminal 27 opening 28 sidewall 29 second wire material 31
convex structure 35 first deflector 36 second aperture 64
emitter-base mount 67 differential exhaust hole 68 vacuum vessel 69
vacuum cutoff valve 70 non-evaporable getter 71 vacuum pump 72
heating mechanism 74 vacuum cutoff valve 76 gas supply mechanism 77
vacuum cutoff valve 78 vacuum pump 91 gas field ion source
controller 92 refrigerator controller 93 lens controller 94 first
aperture controller 95 ion beam scanning controller 96 secondary
electron detector controller 97 sample stage controller 98 vacuum
exhaust pump controller 99 computing device 195 first deflector
controller 196 temperature controller 418 cover
* * * * *